FIELD OF THE INVENTION
The invention relates to a transmission system including a central station connected to a counterpart station, at least two base stations connected to the central station through at least one interface, the base stations wirelessly exchanging signals with at least one mobile terminal station, signals output by the counterpart station being transmitted through the central station and the base stations to the terminal station, and signals output by the terminal station being transmitted through the base stations and the central station to the counterpart station.
Modern architectures of private secondary-station systems allow the connection of base stations by the DECT standard (DECT=Digital European Cordless Telephone) through the use of a digital interface by various methods with a constant or negligible transmit time, such as by the Upn standard, to the central station. The prerequisite is that at the transition of the mobile terminal station from one base station to another during the conversation, the data flow is synchronized at all of the base stations. In that connection, synchronized is understood to mean that the data which are transmitted in one frame by the DECT standard from the central station to various base stations through various interfaces appear in the air with a chronological offset from one another of less than 4 .mu.s.
In order to attain such synchronicity, a synchronizing pulse triggered by the frame clock under the DECT standard is, for instance, transmitted through the Upn standard interfaces to the base stations with a certain delay. At the Upn standard interface, a so-called T-bit is provided. The transmission of the T-bit is chronologically fixedly coupled in a certain way with an integrated services digital network oriented modular (IOM) interface. As a result, the transmission of the T-bit is made possible through a plurality of Upn standard interfaces, which are connected to the IOM interface. That in turn means that those base stations start synchronously.
However, a disadvantage of the Upn standard interfaces is their relatively short range. Interfaces under the Uko standard, for instance, allow a ten times greater distance between the central station and the base station, by comparison. However, Uko standard interfaces have neither a T-bit nor a defined chronological relationship with the IOM interface in the transmission.